The present invention relates to an apparatus for keeping the gap cut by a saw in a workpiece open. More specifically, the invention is directed to metal saws, particularly circular saws for steel and non-ferrous metals such as brass, copper and aluminum. Especially in connection with the non-ferrous metals it happens frequently that the width of the gap or kerf cut by the saw blade decreases as the cutting depth increases thereby clamping the saw blade between the two workpiece portions. This happens as soon as the saw blade has penetrated sufficiently into the workpiece to be cut or when the saw blade has left an open gap behind it, as viewed in the feed advance direction. A similar decrease in the gap width occurs when cutting steel, for example, sectional steel beams, though not as frequently as in connection with non-ferrous metals. This reduction in the gap width is due to the fact that tension forces are freed as the cutting advances, thereby clamping the saw blade possibly to such an extent that the clamping force may become larger than the driving force of the sawing machine, thereby completely blocking the saw blade from further feed advance into the workpiece.
Heretofore, it was customary to free the saw blade by driving wedges into the open section of the sawed gap in order to free the saw blade when such a clamping action occurred. However, it is not always practical to place such wedges.
It is further known to make several cuts adjacent to each other, especially at the end of a workpiece because the clamping tension is even more effective at the ends of a block to be cut. Such several cuts penetrate the workpiece to different depths and are arranged at random spacings from each other, whereby each further cut penetrates deeper and deeper into the workpiece, thereby releasing the tension forces in the workpiece so that the saw blade would not be hindered in performing the final intended cut. Both of the just described prior art methods of avoiding the wedging of the saw blade are time consuming and in the last described approach, substantial material is wasted.
It has also been attempted to solve the problem by means of very sturdy vertical or horizontal clamping devices providing such high clamping powers that a narrowing of the gap made by the saw blade was substantially eliminated. However, here again due to the play of the movable parts and due to their springiness or elasticity a diminishing of the sawed gap width could not be avoided with certainty.
The most effective remedy heretofore, for example, in connection with sawing operations employing circular saw blades having inserted teeth, was to allow the teeth of the saw blade to alternately extend laterally out of the plane defined by the saw blade to one and to the other side and to further shape the teeth to taper radially inwardly from the outer end or tip of the teeth toward the body of the saw blade. Due to this structure of the saw blade, or rather of the teeth of the blade, the width of the cut gap became so large that the circular saw blade was not clamped any more. However, the disadvantage of this approach is seen in that the large width of the sawing gap results in a correspondingly high waste of material for each cut.
Furthermore, there are saw blades available the teeth of which are so constructed that they make a radial and tangential shearing cut so that the saw blade frees itself by its own cutting action in the lateral direction. These blade work excellently but it is difficult to produce them and therefore they are very expensive.